Pollution Prevention and Cleaner Technology in Textile Industry

Pratik Deogekar (110040010)Praneeta Nehra (110040028)Amar Sinha (110040116)Shanshank Bansal (110020050)

Introduction

• Textile industry is based on the conversion of fibres into fabric which is then fabricated to clothes or other artefacts.• In Indian context, it contributes to 14% of the

total industrial production.• It is largest industry in terms of employment

generation.• Magnitude of the industry makes a review of its

environmental performance a necessity.

Textile Manufacturing Process

Conversion of fibres (raw material) into the clothes or other artefacts (finished products) involves the following steps:-•Preparatory process•Spinning•Weaving•Finishing

Preparatory processThis process converts the natural fibre cultivated from the field into a yarn called “Roving”. The stages involved are :-• Ginning – separation of seeds and vegetable matter from the

cotton fibre.• Picking – cotton is beaten to loosen it up, then passed through

rollers to remove any remaining vegetable matter. Then it is blown on a screen by a fan and passed through more rollers to emerge as “lap” (soft fleecy sheet).

• Carding – Tangled fibres are combed and lined up in parallel rows and short fibres are discarded to produce sliver (first stage yarn)

• Drawing – Slivers are straightened and combined to produce thick cotton rope of consistent size called “roving”.

Carding and Drawing machine

http://www.millmuseum.org/exhibits/permanent-exhibits/the-dugan-mill/

Spinning

• The spinning machine takes the roving, thins it and twists it to create yarn which is almost thirty times thinner than the slivers and winds it onto a bobbin. (strength increases)• The thin yarn around a bobbin is transferred

onto a large cone called “cop” by a automated machine.

Weaving

• Two distinct set of yarns or threads are interlaced at right angles to form a fabric or cloth.• A loom holds the longitudinal threads called

“warp”, while the lateral threads called “weft” are woven through them.• Alternatively, knitting can be used where the

yarn is woven in loops to form fabric.

Loom (used for weaving)

http://www.ccm.ece.vt.edu/etextiles/projects/projects_loom.html

FinishingFinal processing carried out before the cloth is released into the market. Processes involved are:-• Desizing – removal of starch from the fabric using dilute acids

or enzymes.• Scouring – removal of natural wax, non-fibrous impurities and

added dirt. The fabric is boiled in an alkali to form free fatty acids (saponification).• Bleaching – whiteness of cloth is improved by removing

natural colour of fibre using oxidizing agent (like hydrogen peroxide and sodium hypochlorite).• Singeing - smoothness of the fabric is improved by passing a

heated plate over the ends of fabric raised by passing them over a brush.

Contd…

• Mercerizing - luster, strength and dye affinity of the fabric are improved by treating it with caustic soda solution.• Dyeing – Colouration of fabric by immersing it in a bath

of anionic dyes. For improved fastness, vats and reactives may be used.• Printing – Localized dyeing by applying colour in form of

ink in predetermined manner.

Waste Generation

• Textile processing generates many waste streams, including liquid, gaseous and solid wastes, some of which may be hazardous.• The type of waste generated depends on the type of

textile facility, the processes and technologies being operated, and the types of fibers and chemicals used.

Water Pollution• In textile industries consumption of energy in form of

water is relatively high, especially in processes like washing, de-sizing, bleaching, rinsing, dyeing, printing, coating and finishing.• Wastewater which is generated by printing and dyeing

units is often rich in color, containing residues of reactive dyes and chemicals and hence requires proper treatment before being released into the environment.• Dyeing auxiliaries or organic substances are non-

recyclable and contribute to the high BOD/COD of the effluents.• The main environmental problems associated with textile

industry are typically those associated with water body pollution caused by the discharge of untreated effluents

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http://www.simem.com/UploadImgs/510_Abishek_4ba.jpg

Water Pollution distribution

http://ec.gc.ca/planp2-p2plan/3944D8AC-944E-4BB6-B4F8-15D10ED3FCD3/X-20080521135207562.jpg

Air Emission• Most processes performed in textile mills produce

atmospheric emissions. Gaseous emissions have been identified as the second greatest pollution problem (after effluent quality) for the textile industry.• Textile mills usually generate nitrogen and sulphur oxides

from boilers• Hydrocarbons are emitted from drying ovens and from

mineral oils in high-temperature drying/curing• Kerosene is released into the atmosphere during

printing, drying, and curing. Air-laden kerosene is harmful to human beings, as well as to the flora and fauna, in the neighborhood.

http://www.indiantextilejournal.com/articles/Includes/IncImages/2420_tab2.jpg

Air emission pollutant source and type of pollutant in each process

Solid Waste• The primary residual wastes generated from the textile

industry are non-hazardous. These include scraps of fabric and yarn, off-specification yarn and fabric and packaging waste.

• There are also wastes associated with the storage and production of yarns and textiles, such as chemical storage drums, cardboard reels for storing fabric and cones used to hold yarns for dyeing and knitting .

Summary of all wastage